Disclosed is a cooking process of red bean sediment for reducing an unpleasant and slightly bitter aftertaste of red beans by removing tannins and saponins contained in red beans through repetition of a water changing operation, a cooking process of red bean porridge with the red bean sediment, and red bean porridge. The cooking process provides enhanced sensory attributes in terms of color and taste of the red bean porridge by minimizing contents of tannin and saponin causing the unpleasant aftertaste of the red bean porridge through a number of water changing operations between boiling of red beans.